Abstract: n recent years, models are increasingly used
throughout the entire lifecycle in software development
projects. In effect, the need for collaborating on these
models emerged, requiring change tracking and versioning.
However, many researchers have shown that existing methods
and tools for Version Control (VC) do not work well on
graph-like models, such as UML, SysML or domain-specific
modeling languages. To alleviate this, alternative
techniques and methods have been proposed which can be
classified into state-based and operation-based
approaches. Existing research shows advantages of
operation-based over state-based approaches in selected
use cases, such as conflict detection or merging. However,
there are only few results available on the advantages of
operation-based approaches in the most common use case of
a VC system: review and understand change. In this paper,
we present and discuss both approaches and their use
cases. Moreover, we present the results of an empirical
study to compare a state-based with an operation-based
approach for the use case of reviewing and understanding
change. For this study, we have mined an operation-based
model repository and interviewed users to assess their
understanding of randomly selected changes. Our results
indicate that users better understand complex changes in
the operation-based representation.